user/test/com/google/gwt/resources/client/gss/eval.gss

@def WHITE eval('com.google.gwt.resources.client.gss.Constants.white()');

.someClass {
    color: WHITE;
    background-color: eval('com.google.gwt.resources.client.gss.Constants.red("blop")');
    width: eval('com.google.gwt.resources.client.gss.Constants.width() - 15 + "px"')
}